Preparation of lower mixed organic esters of cellulose from partially hydrolyzed cellulose acetate



Patented Oct. 4, 1 932 YORK PREPARATION OF LOWER MIXED ORGANIC ESTERS OF CELL'ULOSE FEQh-l PAE'IZALLY CYRIL J. STAUD AND ERIC K. MCLEAIBT, OF ROCHESTER, NEW YORK, ASSIGNGRS TO EAST- MAN KODAK COMPANY, OF ROCHESTER,

new some A conronarron ornnw HYDROLYZED CELLULOSE ACETATE No Drawing. Application filed October 3,

This invention relates to the preparation of cellulose esters of the nature of cellulose acetate-propionate by esterifying partially hydrolyzed cellulose acetate with an esterifying bath containing both the anhydride and the acid of the group, such as propionyl, which is to be introduced into the cellulose molecule.

Heretofore it has been known to propionate or butyrate cellulose acetate by treating it in an esterifying bath containing proplonyl chloride and pyridine. Propionyl chloride which is employed in that process is not readily available on a commercial scale and due to the expense involved, that process has not been carried out to a great extent on a commercial scale.

It has also been known to esterify cellulose acetate with a fatty acid anhydride and chloracetic acid, which is an excellent method of producing mixed esters of cellulose but that method has the disadvantage that chloracetic acid has a decidedly corrosive elfect on the containing vessels in which it is employed.

We have now found a method of making cellulose acetate-propionates and cellulose acetate butyrates which is simple, rapid and easily controlled. We have found a method of making cellulose acetate-propionates which employs a partially deacetylated cellulose acetate such as for example commercially available acetone-soluble hydrolyzed cellulose acetate as the starting material, which is low in cost of materials and operation so as to be of commercial value and which is not corrosive of the equipment which is ordinarily employed for the esterification of cellulose.

We have found a methodof making cellulose acetate-propionate or -loutyrate which makes possible the dispersion of the partially ester-tied cellulose acetate prior toits esterfication thus facilitating the esterification which may be carried out under conditions which are less severe than those which are ordi-, narily necessary to assure the proper esterification of cellulosic materials. We have found a method of making a cellulose acetat 1931. Serial No. 566,794.

lied cellulose acetate having anacetyl content of about 3538% is treated with an esterifying bath containing propionic acid, propionic anhydride and a catalyst, a cellulose acetate propionate is produced wh1ch is equal or even superior to the cellulose acetate-propionates heretofore produced. lVe have found that when the cellulose acetate is pretreated with the propionic acid, it may be dispersed in the 'acid, which condition is advantageous for the subsequent treatment with propionic anhydride and a catalyst.

The following example illustrates one method by which our invention may be carmaintained at about 4050 C. for approximately 16 hours. Thefcellulose acetate is dispersed by this treatment. A mixture of '26 lbs. of propionic anhydride, 10 lbs. of pro pionic acid and .25 lbs. of magnesium perchlorate trihydrate is then added.

The mass is maintained between 5060 C. for about 5 hours. It may then be poured into water with vigorous stirring and the cellulose acetate-propionate will be precipitated out. This ester is soluble in ethylene chlorid, acetone, ethyl acetate, etc.

It is to be understood that our process may also be employed to produce cellulose acetatebutyrate, in which case equimolecular proportions of butyric acid and anhydride will be employed in place of the respective amounts ofpropionic acid and anhydride employed in our process.

The product of our process may be employed for filnnfilamentsetc. from ethylene chloride, acetone or ethylene chloride-alcohol solutions of the same or if desired it may first be hydrolyzed according to themethoddis closed in Malm and Fletcher application Se-' rial No. 551,546 and the product resulting from that process may be employed to pro duce film or sheeting. V y c It is obvious that various modifications of our invention will be apparaent to those familiar with the chemistry of cellulose esters and all such modifications are within the contemplation of the present invention.

WVe claim as our invention:

1. A process of making a mixed ester of cellulose which comprises esterifying a partially hydrolyzed cellulose acetate with a reaction bath containing an acid and the corresponding anhydride each of which contains an acyl group selected from the group consisting of propionyl and butyryl. 2. A process of making. cellulose acetatepropionate which comprises treating a par-' tially'hydrolyzed cellulose acetate with an esterifying bath containing propionic acid and anhydride. V

3. A process of making cellulose acetatepropionate which comprises dispersing a partially hydrolyzed cellulose acetate in pro- 'pionie acid and then esterifying the dispersed cellulose acetate in a reaction mixture containing propionic anhydride. r 7

4. A process of making cellulose acetatebutyrate which comprises treating a partially hydrolyzed cellulose acetate with an esterii'ying bath containing hutyric acid and anhydride. f

5. A process of makingcellulose acetatebutyrate which comprises dispersing aspartially hydrolyzed cellulose acetate in butyric acid and then esterifying the dispersed cellulose acetate in a reaction mixture containing butyrie anhydride. v Q

Signed at Rochester, New York, this 24th day of September, 1931.

' .CYRIL J. STAUD. ERIC K. MoLEAN. 

